“We’ve become a nation of slogan-saying, bile-spewing hatemongers! We’ve lost our kindness! We’ve lost our soul!” shouts Frank (Joel Murray), an aggrieved middle-aged everyman with plenty of reasons to be mad as hell.

In his climactic rant near the end of the fire-breathing comic satire “God Bless America,” Frank is an obvious mouthpiece for the film’s writer and director, Bobcat Goldthwait. Like it or not, his unhinged fury strikes a chord.

A 21st-century Howard Beale toting an automatic rifle, Frank has commandeered the stage of “American Superstarz,” an “American Idol”-like reality show, and demands the camera’s attention. He is outraged that week after week the show has been exploiting a cretinous, talent-free butterball for laughs.

This hapless object of mass ridicule, Steven Clark (Aris Alvarado), who has attempted suicide, achieved celebrity by groaning and flailing through a tuneless version of “Theme From Mahogany (Do You Know Where You’re Going To).”

Frank foolishly believes himself to be the great defender of Steven and his persecuted ilk until that oaf interrupts his speech to explain with a grin that he didn’t try to kill himself because people were making fun of him but because “they weren’t going to put me on TV anymore.”

The key word in Frank’s tirade is “kindness.” Its conspicuous absence on television nowadays galls him to the degree that he begins acting out his unkind urge to mow down people he doesn’t like.

My biggest complaint with the movie is that “American Idol” and talent shows like it aren’t all that evil in the broader scheme of things. The bullying that that show once frequently welcomed was contemptible, but even the most clueless contestants must have had some inkling of what was in store for them.

It would be impossible for any movie to sustain the rage that propels the early scenes here, which show Frank’s steam rising as he channel-surfs through dead-on parodies of “My Super Sweet 16”; “Jackass”; angry right-wing pundits; and all manner of toxic, bottom-feeding television culture.

On top of all that, Frank learns from a doctor that his recurrent migraines are caused by a malignant brain tumor. He is fired from his job for “harassment” after an act of pure generosity: sending flowers to the home of his office receptionist, who wasn’t feeling well. His rude yuppie neighbors in Syracuse (Mr. Goldthwait’s hometown) have a baby that screams all night. And his daughter by his ex-wife, who has remarried, is a spoiled brat who refuses to see him.

After contemplating suicide, Frank decides that because he isn’t long for this world, he may as well vent his misanthropy behind the barrel of a gun. His first victim, Chloe (Maddie Hasson), is the monstrous teenager from the “My Super Sweet 16” parody who flies into a tantrum when her parents give her the wrong car for her birthday. When Frank blows her to bits, you may feel a twinge of guilty pleasure.

While prowling on Chloe’s parents’ estate, Frank is importuned by Roxy (Tara Lynne Barr), a foul-mouthed local girl. After some verbal skirmishing, they become a team of natural-born killers who affect “Bonnie and Clyde” headwear.

There are no police chases or shootouts, just lethal justice meted out to those who “deserve to die.” Aside from Frank, whom Mr. Murray plays with a perfect mixture of righteous indignation, despair and craziness, there are no fully drawn characters. Roxy is a cardboard caricature of a precocious Diablo Cody creation.

Mr. Goldthwait’s screenplay is essentially a comedy act fleshed out with a story he doesn’t try to make convincing. The funniest moments are speeches like Roxy’s twisted argument that every road in today’s rock ’n’ roll landscape leads back to Alice Cooper, whose music is heard on the soundtrack. As she tells it, his pre-eminence makes a certain demented sense. “God Bless America” will make you laugh — up to a point.